Low-density gas clouds, like NGC 6826 (which I studied for my Masters degree, incidentally), emit light in a very different way than stars do; they aren’t blackbodies at all. They are more like fluorescent lights, giving off lights at very specific colors, and not continuously across the spectrum.

If the cosmic gas is hot, and contains oxygen, the nebula can strongly emit light at about 500 nanometers, smack in the green part of the spectrum. They also emit some red and other colors, but they don’t emit across the entire spectrum like stars do. These objects do in fact look very green through the telescope, but remember, they’re not stars!

The planet Uranus looks green too, but that’s because its upper atmosphere has lots of methane, which absorbs red light. Again, it’s not a star so it doesn’t count.

Now, I do have to say, there is a way for some stars to kinda sorta look green. We sense colors not just on an absolute scale, but also by comparison as well. An object that looks one shade of red by itself will look a different shade if you put it next to a yellow object. Your eyes and brain together can be fooled this way.

Almach is multiple star system in Andromeda (though to the eye it looks like just one star), and its components do just this. The brightest star is an orange giant, a star like the Sun that’s dying. It’s cooler than the Sun, and so looks orange to the eye. The other three stars comprising the Almach system are white dwarfs, dead stars that glow due to their leftover heat. Two of them are barely separable by telescope, and the third orbits one so closely it’s impossible to see. But the combined light of these three stars is whitish… but when you look at it through a telescope, with the orange star visible as well, the trinary takes on an emerald green glow! It’s not real, in that it’s an illusion, but it does still look green. Interestingly, in all the images I found, it looks bluish; maybe the camera is not as easily fooled as our brains. Other examples of multiple stars like this can be found, too.

But is there a star that’s intrinsically green? Zubeneschamali is the second brightest star in the constellation of Libra. It’s somewhat hotter than the Sun, and some people claim it looks green to them, while other say it looks white. It’s unclear why; some people’s sensitivities are different, but it might also have to due with the star itself: Zubeneschamali is a young star and a rapid rotator, which might affect its colors (the emitted light from a star is not really a blackbody, and its youth and rotation might have some influence on its emitted colors).

So maybe, maybe, there is one intrinsically green star, but even then it’s controversial.

There are several lessons here. One is that stars really can’t be intrinsically green; they need to be seen against a contrasting color to look green, and even then it’s just a trick. Also, there are green objects in space, but they are very different than stars (gas clouds and planets). And finally, the color we see from an object depends on how that object emits light, which can be just as important as the light emitted itself.

Nice post, Phil! However, I have to do some nitpicking. I don’t think that Uranus is really green to the naked eye, but it just appeared that way in the original releases of Voyager 2 images due to processing. Emily recently linked to Don Davis’ page that deals with planetary colors, and it’s very informative (link below).

Larian:
Close your eyes and take a deep breath. Go ahead…
There.
You just benefited from the work of a planetary nebula like the one in the picture. This is where oxygen comes from. The green glow you see there is from doubly ionized oxygen that is fluorescing under the UV light emitted by the white dwarf you see in the center.

It’s weird. I had to enter that last post twice to get it to appear and when it did it said “Your comment is awaiting moderation.”
What are the rules regarding such automated replies?
Just curious…
Rich

Um.. That picture of the planetary nebula. Is that not one of the HST’s false-color images, where red, green, and blue are due to the brightness of certain lines of elements like hydrogen, oxygen, and nitrogen? (I can’t recall exactly which, but I know that the red is hydrogen.) So it wouldn’t really look green, right? It would look red in a real-color image since hydrogen is the most abundant element in these clouds.

Is it right to say the brain is fooled? Isn’t it more accurate to sat that all colour is subjective, but that usually (but, crucially, not always) what we perceive as green is light around 500nm. In other words, ‘green’ is defined by our experience, and we have found be experiment that most greens have the same physical explanation. There is no such thing as ‘intrinsic’ greenness, there’s only electromagnetic radiation and eye-brain response.

@PG:
You will see some green anyway. As Phil mentioned, one recombination-line of oxygen is roughly at 500nm which is in the green part of the visible spectrum. So, if there is oxygen abundant in the cloud you will see some green….

@Nathan:
You mean that there is a plasma, again, right? I don’t know if you read my posts in the other blog entery, maybe my english is too bad (I’m sorry!)….. But: Of course the “gas” is a plasma, right! But the motions of the particles are NOT aligned, they are random! So there is no current resulting in no electromagnetic field. So the plasma will (on large scales, as we can always (or mostly) asume in astrophysics) behave just like a gas, a hot gas. It is ionised, of course. It has to be! Because would it not be ionised, there would be no recombination and no radiation and we could not see the whole thing (ok, there could be some blackbody radiation but we may leave this out, now).
Hopefully my english was well enaugh that I could made my point clear. Maybe 😉

@DrFlimmer: [begin a bit of pedantry] the abundance of Hydrogen is about 10,000 times greater than that of oxygen in these nebulae. So there’s some green (if just a tiny bit). I’m just saying that the green would not be visible if you looked at the object in true color, and all you’d see is the overpowering red of the H-alpha line at 626nm (the HST people have “cranked up” the green to bring out the details in the compositional information). Everything Phil said is right, I just wanted to point out to the general reader that the photo is somewhat misleading (even if they did use HST images like these in Star Trek: Voyager!) [pedantry complete!]

The Orion Nebula has always appeared distinctly green to me through both my small refractor and my 8″ reflector. (Size does not seem to matter. Er. Ahem.) It’s considerably different from other bright nebulae, for instance the Lagoon or the Omega, which appear very neutral. At least to my eyes, which are admittedly kind of wonky.

@PG
It’s not just the relative abundance of hydrogen to oxygen that determines if something looks red or green. The rate of emission (how many photons are emitted per atom per second) which depends on quantum mechanics of that line and things like the temperature and pressure of the gas/plasma and what radiation (usually UV from hot stars) is hitting the gas/plasma. (For example, A-type (white) stars have the strongest visible-light hydrogen lines (dark against the background blackbody), while both hotter stars and cooler stars have weaker or absent lines — not because they have less hydrogen, but because the temperature changes the state of the hydrogen’s electrons.) In fact, for many nebulae, the boundary you see might not be the extent of the gas, but the place where conditions change from where the atoms are in the right state to where they aren’t.

Then you have to consider the human eye (or film, or CCD), which is more sensitive to different parts of the spectrum — I know CCDs show the Orion Nebula as red, while most people who look at it through a small telescope will see it as green.

Aaaaanyway. I was also wondering about whether the image is a true-color one. I think we’re so used to the Hubble palette that we forget about it sometimes.

It doesn’t say either way in the image info:

ABOUT THIS IMAGE:

NGC 6826’s eye-like appearance is marred by two sets of blood-red “fliers” that lie horizontally across the image. The surrounding faint green “white” of the eye is believed to be gas that made up almost half of the star’s mass for most of its life. The hot remnant star (in the center of the green oval) drives a fast wind into older material, forming a hot interior bubble which pushes the older gas ahead of it to form a bright rim. (The star is one of the brightest stars in any planetary.) NGC 6826 is 2,200 light- years away in the constellation Cygnus. The Hubble telescope observation was taken Jan. 27, 1996 with the Wide Field and Planetary Camera 2.

@DrFlimmer: “But the motions of the particles are NOT aligned, they are random! So there is no current resulting in no electromagnetic field.” That’s an assumption, based on no evidence and no reason beyond that it might be inconvenient if it weren’t so. There’s no honest reason not to just call it what it is, but plenty of dishonest reasons.

The human eye is not very sensitive at all to H-alpha emissions at 656.3 nm, and is much more sensitive to O-III emission at 500.7 nm. So even if more H-a light is produced, the human eye may see the green colour more clearly. Hydrogen may also produce H-beta emissions at 486 nm, adding a blue-green colour.

Ha, it kind of reminds me of the sanity guardian from Eternal Darkness. Pareidolia are great.

Keep up the hard science articles Phil, the earth needs as many good science writers as we can get.

Off topic, but where is your email address listed? I can’t find it anywhere on the site and I have a couple of questions for you if they’re not too much trouble. Just email it to the address I put in to post this or post directions to the right part of the site in this thread. Thanks.

When I read the first thread, which disclaimed green stars, I wondered about human color blindness and the other condition. The other condition makes it difficult to read numbers of one color in a plate of dots of mixed colors.
Wouldn’t a color id disfunction cause that person to see a green star?

About M52. I’ve viewed it through 6×30 and 10×50 binocular; and through both my 60mm refractor and 8″ reflector (all gone, but the 6×30 binocular).
Everytime I looked at the Orion Nebula, it looked white, to me. I’m always facinated by the Trapezium constellation in the nebula. I could get to be a deep space observer, if I don’t watch myself. smile

When I get caught up with some bills, my next set up (binocular, adaptor and camera tripod) will be with a 12×60 binocular; and my next ‘scope will be an 80mm short tube refractor. But, that waits, until I get bars on my windows. I have no plans for another medium reflector.

@Nathan Myers
Quite right. That is exactly what my son has, colour vision deficiency, and “who knows” is exactly his response to any red/green question. He never knows if we are watching grass court tennis from Wimbledon or clay court tennis from Roland-Garros!

Well, that gave me a smile 😉 (“hot ice”)…. In some way you are right. Why not call it a plasma, when it is one… but there are some things I want to add:

One: astronomers are a “wierd species”, because they call everything as they want. Heard an astronomer use the word “metal”? Do you know what he means? Not only iron and copper. He means EVERY element which is heavier than helium, so he also means oxygen, carbon, neon, and so on. These are elements normally not known to be “metals” – but astronomers call them that way.

Two: I count on thermodynamics. Temperature has something to do with the kinetic energy of particles (or with the speed of them). And the speed (and I don’t say velocity here because the motions are NORMALY not aligned and thus have no “overall” direction) is distributed like a Maxwell-distribution – but, again, not aligned. This works for all the air around you, I guess you will agree with me here.
Now the plasma: Take an interstellar gas-cloud (intergalactic gas-cloud is also possible). It won’t be very warm unless there is something to heat it. If it’s heated then the particles will start to “move” randomly according to the laws of thermodynamics, and, if the (heat)radiation is energetic enaugh, the atoms will be inoniesed according to quantummechanics. So, we gain a plasma with partcles moving randomly, right?
So now electrodynamics: A current (especially a changing one) induces a magnetic field and changing magnetic fileds (and seperated electric charges, of course) induce an electric field. What we need is a current. A current is an ALIGNED motion of charged particles (i.e. electrons) with respect to other (charged) particles (i.e. ions). If a plasma moves that way, you need magneto-hydro-dynamics to describe it properly.
But here is the point: Our gas cloud was at rest (we can assume that – just place yourself in the frame of rest of the gas cloud). Here comes the heating – the atomes get ionised and begin to move randomly due to the heat. If we have no “external” force to seperate the electrons and the ions from each other there will be no aligned motion and thus no current. What will happen is that the ions will capture another electron (-> recombination) and will emit light what we can detect. Then comes another photon and will re-ionise the atom which will recombinate again – and so on.
What we get here is a cloud of particles becoming ionised and neutralised again. There is a plasma, of course, but electric fields do not become larger than the Debye-length, so overall there is no current.

And why produced I this long text?
Well, finally: There is no need to describe the plasma with magneto-hydro-dynamics. Overall it will behave according to the laws of thermodynamics (like a GAS), just with a little quantummechanics (ionisation recombination). And referring to point ONE, astronomers don’t see the point why they shouldn’t call a thing behaving like a gas just as a “gas”.
This is all about a “strange naming” by astronomers and a plasma behaving like a gas.

Is Almach a true multiple star system with all 4 stars being gravitationally bound to each other?

How does the orbit look like? Is it weird? Or just 2 in the centre with 2 revolving around them?

Talking about multiple star system: What is a reasonable range for the angular diameters of the suns as viewed from a hypothetical planet within the habitable zone?
(That scene with two suns in StarWars freaks me out, for multiple suns not frying the planet surely must imply that one appears much smaller, right?)

Imagining that all four stars were still in their prime (i.e. not white dwarfs), then what would reasonable angular diameters be for a planet within the habitable zones of such as system?

@ shane
What is Roger Federer (Swiss)if not European? ( He won five Wimbledon finals in a row) and Nadal (Spanish) won four French open finals in a row and then won Wimbledon this year! In fact in Europe we haven’t seen a Yank (Roddick)or an Aussie (Hewitt) win in quite a while

Green stars do exist and are cataloged. Phil, I’ll bet you an ice cream Sundae on this.

[Note to any reader: please don’t quote me just yet on this.]

For more on this topic, someone once wrote a great article in Astronomy magazine called “Alien Skies” that gave good evidence for green tendrils in space. That someone was….. ta dah! The Bad Astronomer.

That’s an assumption, based on no evidence and no reason beyond that it might be inconvenient if it weren’t so. There’s no honest reason not to just call it what it is, but plenty of dishonest reasons.

First, it is seriously offensive to call science and scientists dishonest, when the whole process is set up to guarantee that it won’t happen much.

Second, as DrFlimmer so eloquently have described it, it is AFAIU a universal process that produces this; you don’t even have to resort to parsimony to explain why neutrality is the default expectation.

Besides, there is the observational evidence. If there were organizing currents I would expect it should show up as recognizable doppler shifting of the emissions. (Which, as we heard in the post, can be distinctive as regards spectra.) I assume that there is no evidence of that in these types of systems.

Overall it will behave according to the laws of thermodynamics (like a GAS), just with a little quantummechanics (ionisation recombination).

And perhaps a dash of classic EM? A plasma would have a sheath region at the boundary, which explains why electrons doesn’t leak away. (As a leak will set up a positive counter potential on the plasma.)

Btw, I believe you want to say your “recombinate” should technically be “recombine”, as in “the atom will recombine again”? And my spell checker insists that it is “ionization” in Phil Plait’s US english. [And for my part it is “Doppler shifting” after the scientist of course, but I think it is a capital bore to bear with english capitalization. ;-)]

Btw:
My explanation works exactly in so-called “HII-Regions” (H-two). (Check it out somewhere…)
And here we have the same “strang naming” again. Because the “II” stands for “once ionised” – it’s clear and obvious, right? 😉 As you can guess… a “I” stands for a neutral atom, hydrogen can only be ionised once (so HII is a fully ionised hydrogen-gas/plasma), a fully ionised helium-gas/plasma is an “HeIII”-gas, and so on … got it? Good

Phil:
Your explanation of the stars system Almach brought to mind an experience I used to have way back in the prehistoric days of the Apple IIc computers.
While working on all nighters getting seminar papers done and a thesis written, I would be staring at a green-on-black Apple II screen for hours. Every so often, I’d have to look up and the white walls of my office and the papers with my notes would almost glow an orangy-pink. The first few times, I blamed it on cheap caffein.

Later I realized it was some sort of color compensation. I understand that is why surgical scrubs were changed to from white to aqua green, because after staring at the red insides of patients, surgeons would find all the whiteness around them turning green and it was pretty dizzying to some.

First of all: THANKS!
And the dash of EM…. well, you can do it if you like, but it is not necessary to take the “boundaries” into account in most cases. The most “interesting” things will happen in the whole cloud. And the clouds can be VERY big (few parsecs or even bigger!). So boundary-effects will be quite negligible.

This is another thing in astrophysics: Not only strange naming, but also what is considered negligible or what is a good “error” in your calculations. 20% error is quite good because you have no choice to remake your “experiment”. And due to the large scales of most astrophysical objects (like gasclouds, stars, galaxies or the universe itself) there is no need of regarding every “little boundary” all the time.
It also depends on what you are looking at. I.e.:
Space is a perfect vacuum, even near to earth. But if you study the behaviour of the atmosphere and the magnetic field you have to take the few particles (5 pccm) into account (compared with 10^23 pccm on the surface of the earth!!).

Sorry for yelling, and I apologize in advance for posting something irrelevant to the topic. I’m only posting here since I think Phil reads these posts. So… Phil, (or anyone in the know) where did the Ed Mitchell-UFO post go? You know, the one with the big Michael Horn debate. There were a few people (Todd, Greg in Austin, Celtic etc.) that spent a lot of time building a great case for critical thinking. Will comments continue to disappear in the future like that? I’m not overly worried about it since I only chimed in every now and then on that particular post, but I feel bad for the folks that typed pages and pages to prove their point, only to have them vanish. Michael Horn included. Or maybe the problem is with my browser… but I can’t find anything. And yes, I’ll feel like a toolbox for posting this if the problem is on my end. Thanks in advance. If you could, please post here rather than email me since I gave a fake email address. Damn spam… thanks.

Glad to know it’s not only me having issues. I paged back to the original article thinking that maybe I had a bad link bookmarked, but the 1098 comments that are supposed to be with it are gone. It’s sad really, and I bet some people will now be hesitant to write lengthy and informative posts when there is a possibility of them disappearing at any given moment. 1098 comments disappearing = a lot of wasted time for a lot of folk. Such a disservice. Maybe Phil can smack an I.T. guy around at Discover and get it fixed.

Okay, I should have considered that electron leakage and concurrent small positive potential is a very, very, … , very minuscule part of the description of plasmas light years across. [I have grown up amongst mesoscale cold plasmas, in plasma processing systems.]

Um, now I see this picture of plasmas without sheaths, as in “bare”. Slightly pornographic IMO. 😛

C’mon, dudes. Open your eyes. Those UFO posts didn’t disappear…they never existed! At least that’s what the Government wants you to believe. Trust me, this was predicted by Billy Meiers back in, oh, 1842. Sheesh.

Probably not an illusion, but given the nature of the “other side” of the argument, no doubt fairly pointless. I wonder what it’s like to debate with people who actually might be open to reasoned persuasion? Oh well, as Mr. Gumby would say, “My brain hurrrrrrts!”

@DrFlimmer: Your explanation is familiar. However, it amounts to what I said; i.e., if you assume at the outset that only thermal processes can possibly be occurring, your conclusion will be that only thermal processes are occurring. In the meantime, you should know that when you say “MHD”, you’re referring to a profoundly unphysical approximation whose only merit is that neatly avoids the details that make real plasma interesting. (A unit of MHD seems to be part of the standard astronomy curriculum, which may be worse than no exposure at all; ignorance is easier to fix than knowing what “ain’t so”.) If you call all plasma “hot gas”, and all charged-particle motion “rains” or “wind”, you program yourself not to perceive profoundly interesting phenomena happening right under your figurative nose. I expect it will be another two generations before astronomy students are allowed to mention them without being called nasty names by Phil and his brethren.

@Don: Actually that’s madge’s son. But it’s genetic; I presume there are damaged genes on the X chromosome. Maybe the corresponding proteins could be provided, but you’d need to get the right cells to take them up. Someday the requisite genes might be packaged in a virus coat that targets at the right cells, and arranged to be expressed in the right amounts and places, but it doesn’t seem easy.

One of the more famous aspects of these green planetary nebulae was the discovery of the green emission line at 500.7 and 495.9 nm by Huggins in 1864. These lines defied explanation for over fifty years, lending speculation they were due to a new element, which was named nebulium. In 1927, Ira Bowen proposed these lines were formed by otherwise ‘forbidden’ transitions between meta-stable atomic states of oxygen and nitrogen. In 1931, the transitions were demonstrated under laboratory conditions.

More about the history and similar connections in the paper linked on the website above “The Cosmos in Your Pocket: How Cosmological Science Became Earth Technology”.

Wrote the BA :
“The planet Uranus looks green too, but that’s because its upper atmosphere has lots of methane, which absorbs red light. Again, it’s not a star so it doesn’t count.”

But wait Ouranos (to use the proper Greek spelling of this Greek named celestial “wanderer”) *is* in fact listed as a star!

Really. I do believe Flamstead first originally included it on his charts as ’34 Tauri’ – that was of course before Wilhelm Herschel detected “comet” Ouranos (or Georgium Siderus – “George’s Star” – as he wanted to call it in honour of King George III!) on the 13th March 1781 before it’s planetary nature was finally determined. 😉

Much the same thing also happened with Neptune too …
Actually I think several astronomers mistook Ouranos for a star back before Herschel’s official discovery of that planet.

these lines were formed by otherwise ‘forbidden’ transitions between meta-stable atomic states of oxygen and nitrogen

Yet we hear that the thermodynamical behavior of nebulae is lacking “interesting” physics.

@ Nathan Myers:

if you assume at the outset that only thermal processes can possibly be occurring, your conclusion will be that only thermal processes are occurring.

Now you are misrepresenting the commenters as well. DrFlimmer covered the EM processes in his description.

But even if it were true, if the model predicts the data, and there isn’t a competing model, it is correct. You don’t need to assume all possible processes when explaining, say, why a dropped stone fall to the ground.

you should know that when you say “MHD”, you’re referring to a profoundly unphysical approximation

Duh! It predicts physical data, so it is physical.

Perhaps you mean to say that there are more realistic models, in the sense that they are more fundamental.

But surely that can’t be a beauty criteria when comparing similar models – we know that, say, GR is an effective as opposed to fundamental theory of gravitation, yet we don’t go around to call it “a profoundly unphysical approximation” that “avoids the details that makes real” gravitation “interesting” when we lack better models.

Btw, I would like to have a description of what you see as “the details that make real plasma interesting” and how it applies to observations of interstellar plasmas. Just to see if we can agree on the observed facts.

We understand each other 😉 I was about to say the same.
One point I can add (maybe two) : The densities in a gas cloud in outer space are really low. In every earth-bound experiment they would be a “more than best” vacuum with about 10^6 particels pccm. And as I said these clouds are LARGE.. many parsecs across (and no, parsec is not a time-scale as Star Wars implicates 😉 – the same as is with lightyears, they are both length-scales!). These are conditions an earth-bound plasma cannot achieve! So the conditions are different and there is no need to use every single piece there is about plasmas.
And there is the second point, allready mentioned by Torbjörn, but I want to emphasize it:
There is NO need to refer to the “deepest and most fundamental” theory available. We have GR but Newtonian Gravitation works VERY well for earth, so why not use it? It is easier to calculate it than GR, MUCH easier! (Ok, agreed. For GPS we actually need GR!) And so it works with everything else in physics.
Because this is what Physics is all about: The ability to reduce your problem as much as you can and to make it as easy as you can to calculate something. This is how physics differs from mathematics.
Physics is mostly a linear approximation – as long as it works. Mathematician will run out the door screaming seeing such crimes against mathematics ;). But it works and describes the world as we see it. If we cannot hold to it anymore, we will look what the quadratic approximation will yield and so on.

Oh… and one last thing:

Torbjörn: The link you postet leads to an article about physicists of the Ruhr-University in Bochum, Germany. Well, this is exactly “MY” university, where I am studying in the 3rd year 😉

Probably not! Those gas clouds are dense for space conditions, but a perfect vacuum for earth conditions. I guess a space craft would not notice it anyway.
On the other hand: If you have some high-energetic particles in that gas, they would be a threat for the spacecraft – same as solar flares.
But under “normal” conditions I think they are not very effective…. unless those clouds behave as in StarTrek, of course 😉

I’m just curious as to what effect a gas cloud like this would have on a spacecraft flying through it, if any? Would it be even noticeable?

According to NASA, the International Space Station (ISS) orbits at nearly the same height as aurora borealis/australis, sometimes passing over them, and sometimes right through them. However, the auroral electron and proton streams pose no direct danger to the ISS.

Copy and paste the URL below to see for yourself. I could provide a direct link, but it will take ‘forever’ to get it moderated on a Sunday!

Damn it! I tried to submit an answer to Michael L’s question without a direct URL link to source, but it STILL got held up for moderation!

So, I’m submitting my answer again without the bloody URL!

Michael L:

I’m just curious as to what effect a gas cloud like this would have on a spacecraft flying through it, if any? Would it be even noticeable?

According to NASA, the International Space Station (ISS) orbits at nearly the same height as aurora borealis/australis, sometimes passing over them, and sometimes right through them. However, the auroral electron and proton streams pose no direct danger to the ISS.

For some reason the “blockquote” HTML didn’t work properly in my previous comment (“awaiting moderation” at the time of writing this) before last. I wish the web-master of this site would provide commenters with the falcility the edit/delete one’s comment, as is available on RichardDawkins.net.

ERRATUM: For some reason the “blockquote” HTML didn’t work properly in my previous comment (”awaiting moderation” at the time of writing this) before last. I wish that the web-master of this site would provide commenters with the falcility to edit/delete one’s comment, as is available on RichardDawkins.net.

As noted along with Almach are a few other multiple green stars where at least one component appears emerald. The companions to Antares – Antares B which is a type B “blue dwarf” star – and also Rasalgethi B (Alpha Herculis B) again the dimmer B type companion to a red supergiant – both appear green or green-ish to at least some observers.

Zubeneschmali (Beta Librae) is also a type B star, B8 to be precise, which is exactly the same spectral class as Rigel which appears quite bluish although Zubeneschmali is a core hydrogen burning or main sequence (luminosity class V) dwarf unlike Rigel which is instead a core helium fusing bright supergiant (luminosity class Ia) star. Another example of a brightish B8 V star – also a single blue dwarf is Sirrah or Alpheratz (Alpha Andromedae) which again appears bluish white and NOT verdant environmental in hue. Rigel’s companions – that star is actually at least a triple star system of the main supergiant (Rigel A) and two dwarfs (Rigel B & C) both B9 V stars – both usually described as blue or white.

For me personally, Zubeneschmali does sometimes appear green although at other times appearing white – not sure whether imagination and or atmospheric affects are in play here too!

Incidentally, located about 2 degrees from Zubeneschmali is Gliese 581 (aka Gl 581 or GJ 581) that nearby red dwarf star with the much hyped “earth-like” exoplanet (although its more likely to be a supersized Venus than anything “Earthlike”; probably more a Venus-crossed-with-Neptune in fact.) This is very close in the sky to Zubeneschmali but despite its nearness to us, Gliese 581 shines at only magnitude 10.6 in our skies, far dimmer than the faintest objects (mag. 6) visible to the unassisted eye. Gliese 581’s three exoplanets are, of course, well & truly undetectable without specialised equipment but just knowing they’re there is pretty neat!

As well as the Greenness factor and the nearby Gliese 581 planetary system, Beta Librae – Zubeneschmale as its also sometimes spelt (the name means “northern claw’, a reference to the nearby constellation of Scorpius to which all the stars in Libra once belonged.) – has one further distinction :

It is one of the few stars thought to have changed brightness over historical times. Zubeneschmali was once described as being as bright as Antares – as I’ve noted also in that first “no green stars?” thread. Whether or not that has anything to do with its famed emerald glow is another question … Could it have? Anyone?

One thought may be that a massive Coronal Mass Ejection from Beta Librae perhaps left a surrounding cloud of gas scattering & dimming its light to make it seem green? What do folks reckon?

Finally, its also worth noting (again, again) that our own Sun does sometimes appear green – albeit just for a fraction of a second or so during the Green flash! 😉

IVAN3MAN said on August 31st, 2008 at 12:34 pm :
“ERRATUM: For some reason the “blockquote” HTML didn’t work properly in my previous comment (”awaiting moderation” at the time of writing this) before last. I wish that the web-master of this site would provide commenters with the falcility to edit/delete one’s comment, as is available on RichardDawkins.net.”

Hear! Hear!

I couldn’t agree more – in fact I’ve (StevoR too) been calling for this for ages!

The link to Kaler’s ‘Zubeneschmali site is the same one listed by the BA already under the first word of this :
“Zubeneschamali is the second brightest star in the constellation of Libra. It’s somewhat hotter than the Sun, and some people claim it looks green to them, while other say it looks white.”

I should have checked the link at the top of this article *before* I made my last post – which btw. hasn’t yet come through here – although it has according to the “duplicate comments” filter (because I tried to post it again thinking it hadn’t worked ..) Ah, the frustrations of this blog comments thingummy – not meaning to seem ungrateful because I love this blog & forum thingy! 😀

But ..well.. there are some things that could be done better here too!

Out of sheer morbid curiousity, why is it posts here sometimes appear the “awaiting moderation” disclaiming message & other times just don’t show up at all – at least for a while?

Please, could we get some consistency on this? (Personally, I’d prefer the ‘awaiting mod’ message – so we know where we stand & can see that what we’ve posted has come through.)

A better, quicker way of indexing old items / posts here would be nice too as would a html capabilities list – or better yet having the italics, bold etc .. icon buttons a la normal computer typing without needing the > < whatever brackets – &needless tosay lamost – if only we could edit or at least preview our posts.

Oh & getting the old site back would be betetr too or atvery least telling the "Discover" mob to provide us with some left hand margin not allsquashed itno the side format would be nice as well!

Not meaning tocomplain but just giving some hopefully constructive criticism for the Bad Astronomer & others to consider. Either way, many thanks for an eccellent blog anyway.

PS. 1 more thought for the Bad Astronomer any chance some of the best posts here could be compiled into a non-fiction book in themselves?
😉

I’d rather the printed form & a good book than feel stuck to an annoying, slow to load, frustrating, unreliable, @!@#!@!!#@!% computer anyday! 😉

… Of course the book (I’d suggest ‘Best of the Bad Astronomy blog’?) wouldn’t stay as up to date like the blog does but then the posts that survive the test of time & are particularly informative & interesting would remain and people would be able to easily find, catch up on & stumble across ones they might have missed!

Book form does have its advantages too – you could, for example compare all the “best photos of year X” columns easily & see how some stories have evolved over time and much more. Plus they’re easier & more fun to read on the train, in bed, etc ..

So for what little its worth, here’s ten or so superb articles which Dr Phil Plait has written & posed here which I’d suggest deserve proper publishing and including in this hypothetical book for example :

4) This & the previous “No Green Stars?” threads.
(Which btw. I consider two of your best ever, BA! )

5) The Gliese 581 “earthlike” exoplanet thread

6) The “Welcome our Tiny Family” “thread (The borderline star or brown dwarf with low mass planet -MOA-2007-BLG-192Lb) & some of the other threads on exoplanets such as mapping one of the Hot Jupiters, etc ..

7) Some of the pareoilda threads eg. the face in the A-bomb, in the wood, “angel” at the fair ground etc ..

8) Those GLAST ..er ..Fermi threads where you note your own involvement in science.

9) Some of the Pluto / Planetary Definition threads & also the KBO /TNO discoveries like Eris – which I’d call the tenth planet as Pluto is the 9th planet* & Sedna (BTW. Did you post on Sedna, BA?)

Of course, there’s also far more you could include – enough for quite a few “Best of the Bad Astronomy blog” books in fact. So we could have Book I, Book II, Book III, etc ..! 😉 8)

Please <Bad Astronomer I really reckon this is worth considering & would help you reach a wider audience as well as just on-line folks.

* Yes, I know there’s also planet Ceres to include which I’d call the 4 & a halfth planet – just like Isaac Asimov did! Planets : the more the merrier! 😉
________________________

“… he had left out a planet. It was not his fault; everyone leaves it out. I leave it out myself when I list the nine planets, because it is the four-and-a-halfth planet. I’m referring to Ceres; a small but respectable world that doesn’t deserve the neglect it receives.”

DrFlimmer: I wonder where you would find a perfectly uniform non-ionized gas cloud to heat up radiatively into a purely-thermal neutral plasma cloud. In every cosmological model I know of, ionized is the starting state of every scrap of (hadronic) matter in the universe. Uniform and history-free is hard to come by. A non-uniform plasma cloud (i.e., any real cloud, anywhere) is necessarily laced through with sheaths, as broken up into cells as a slime-mold. No, you don’t get to neglect sheaths.

About MHD: a model that is incompatible with Birkeland currents can hardly be called first-order; it’s more akin to Aristotelian gravity than Newtonian. We don’t “lack better models” than MHD; we have PFD, in which empty space is not infinitely conductive. It’s perhaps unfortunate that it’s “fiendishly difficult”, but surely that’s the astronomers’ problem, not the plasma’s.

Yes, of course “plasma” is the starting state of the cosmos. Just think about the tremendous temperature. But roughly 300.000 years after the Big Bang the temperature was too low to be able to ionise anymore. So the protons and electrons recombined to neutral atoms which then just “sat” there and waiting for dark matter to attract them (if I may say so 😉 ). So there are our neutral atoms.
Later came the age of “reionisation” which, of course, didn’t reionised ALL atoms. It was the age of the first stars to come up.
Well. I know that the intergallactic medium is mostly hot gas (plasma). I must say I don’t really know where it gets its energy from – maybe “galactic” friction (tidal forces, etc).

What I was refering to with my description above where HII-regions, regions of star formation. O and B stars are so big that they have a short and very violent life. Theire surface temperature is quite high. In fact it is high enough to ionise the surrounding hydrogen (the photon energy is mostly higher than 13,6eV). But Hydrogen is optically thick to UV-light. So all the emitted light of the star will be captured. Assuming a uniform distribution of the hydrogen around the star the ionised region is well defined by the “Strömgren-sphere” which gives a hint about the size of the ionised region (the HII-region).
We are able to detect the HII-region because of the recombination which will happen like a cascade of the electron down to the ground state in the hydrogen atom. The likeliest transition will be from state 3 to state 2 (in the optical spectrum!) which is the H-alpha-line at roughly 650nm.
So this is the model. Of course it won’t be that easy out there. You have to take into account that the distribution is not unifiorm, angular momentum must be considered. But most of the story is in the described model above.

And again: Those gas/plasma clouds are extreamly big!! Sheaths are indeed quite negligible (if you just stick to the center, for example).

And once more: It is neither always necessary nor is it useful to refer to the “best” model you have if you are able to explain what you see with an “easier” one. If you come to a point where your easy model cannot go further – ok, stick to the “better” one.

I must also confess that I never heard of PFD (also a short check via wikipedia and google didn’t help). Would you tell me what it is, please?

Well, I read through a thread about “plasma cosmology” at JREF for over 2 hours now. Quite interesting (not the idea itself but the discussion 😉 ). Assuming that earth-bound physics aply everywhere unless it is gravity – well, that is… (I don’t know a word), weird.
I guess I have an idea what this stuff is about, thank you for that! I haven’t heard of that stuff until now, and cosmology is a thing I am very interested in… PC hasn’t found the way to Germany yet, or I am visiting the wrong sites ;).

kuhnugget: I’m no fan of “woo-woo” either. Unfortunately dark matter and dark energy are the father and mother of all woo-woos.

DrFlimmer: PFD = plasma fluid dynamics. I wouldn’t know where to find a uniform or symmetric distribution anywhere in this universe. (Remember when a supernova was supposed to be spherically symmetric? Quaint, no?) . It doesn’t matter how big the cloud is, or what’s at the “center”. The action is at the cell boundaries.

It’s easy, if it’s what you prefer, to ignore effects; just ignore effects. It’s extremely popular, nobody will criticize you. But it’s not science.

It amuses me to contemplate stars heating the ISM gravitationally. You are aware, are you not, that it’s a conductive medium moving in the galactic magnetic field? Can you suggest how you would prevent current flow?

In trying to figure out how photosynthesis might operate on other planets, the first step is to explain it on Earth. The energy spectrum of sunlight at Earth’s surface peaks in the blue-green, so scientists have long scratched their heads about why plants reflect green, thereby wasting what appears to be the best available light. The answer is that photosynthesis does not depend on the total amount of light energy but on the energy per photon and the number of photons that make up the light.

Whereas blue photons carry more energy than red ones, the sun emits more of the red kind. Plants use blue photons for their quality and red photons for their quantity. The green photons that lie in between have neither the energy nor the numbers, so plants have adapted to absorb fewer of them.

The basic photosynthetic process, which fixes one carbon atom (obtained from carbon dioxide, CO2) into a simple sugar molecule, requires a minimum of eight photons. It takes one photon to split an oxygen-hydrogen bond in water (H2O) and thereby to obtain an electron for biochemical reactions. A total of four such bonds must be broken to create an oxygen molecule (O2). Each of those photons is matched by at least one additional photon for a second type of reaction to form the sugar. Each photon must have a minimum amount of energy to drive the reactions.

The way plants harvest sunlight is a marvel of nature. Photosynthetic pigments such as chlorophyll are not isolated molecules. They operate in a network like an array of antennas, each tuned to pick out photons of particular wavelengths. Chlorophyll preferentially absorbs red and blue light, and carotenoid pigments (which produce the vibrant reds and yellows of fall foliage) pick up a slightly different shade of blue. All this energy gets funneled to a special chlorophyll molecule at a chemical reaction center, which splits water and releases oxygen.

The funneling process is the key to which colors the pigments select. The complex of molecules at the reaction center can perform chemical reactions only if it receives a red photon or the equivalent amount of energy in some other form. To take advantage of blue photons, the antenna pigments work in concert to convert the high energy (from blue photons) to a lower energy (redder), like a series of step-down transformers that reduces the 100,000 volts of electric power lines to the 120 or 240 volts of a wall outlet. The process begins when a blue photon hits a blue-absorbing pigment and energizes one of the electrons in the molecule. When that electron drops back down to its original state, it releases this energy—but because of energy losses to heat and vibrations, it releases less energy than it absorbed.

The pigment molecule releases its energy not in the form of another photon but in the form of an electrical interaction with another pigment molecule that is able to absorb energy at that lower level. This pigment, in turn, releases an even lower amount of energy, and so the process continues until the original blue photon energy has been downgraded to red. The array of pigments can also convert cyan, green or yellow to red. The reaction center, as the receiving end of the cascade, adapts to absorb the lowest-energy available photons. On our planet’s surface, red photons are both the most abundant and the lowest energy within the visible spectrum.

So plants are green on Earth surface because they absorb such photon energies with slightly less efficiency. Meanwhile they have other colors elsewhere:

For underwater photosynthesizers, red photons are not necessarily the most abundant. Light niches change with depth because of filtering of light by water, by dissolved substances and by overlying organisms themselves. The result is a clear stratification of life-forms according to their mix of pigments. Organisms in lower water layers have pigments adapted to absorb the light colors left over by the layers above. For instance, algae and cyanobacteria have pigments known as phycobilins that harvest green and yellow photons. Nonoxygen-producing (anoxygenic) bacteria have bacteriochlorophylls that absorb far-red and near-infrared light, which is all that penetrates to the murky depths.

We understand that green plants are adapted to the modern atmosphere:

Plants are adapted to this spectrum, which is determined largely by oxygen—yet plants are what put the oxygen into the atmosphere to begin with. When early photosynthetic organisms first appeared on Earth, the atmosphere lacked oxygen, so they must have used different pigments from chlorophyll. Only over time, as photosynthesis altered the atmospheric composition, did chlorophyll emerge as optimal.

Finally, as in contrast to Hoyle, we know how photosynthesis evolved on Earth:

The firm fossil evidence for photosynthesis dates to about 3.4 billion years ago (Ga), but earlier fossils exhibit signs of what could have been photosynthesis. Early photosynthesizers had to start out underwater, in part because water is a good solvent for biochemical reactions and in part because it provides protection against solar UV radiation—shielding that was essential in the absence of an atmospheric ozone layer. These earliest photosynthesizers were underwater bacteria that absorbed infrared photons. Their chemical reactions involved hydrogen, hydrogen sulfide or iron rather than water, so they did not produce oxygen gas. Oxygen-generating (oxygenic) photosynthesis by cyanobacteria in the oceans started 2.7 Ga. Oxygen levels and the ozone layer slowly built up, allowing red and brown algae to emerge. As shallower water became safe from UV, green algae evolved. They lacked phycobilins and were better adapted to the bright light in surface waters. Finally, plants descended from green algae emerged onto land—two billion years after oxygen had begun accumulating in the atmosphere.

Dust would tend to produce some thermal photons, but it is still a huge difference between cold molecular clouds ~ 10 K to habitable atmospheres ~ 300 K. Famously bacteriochlorophylls are purple, not green, red, yellow or brown.

Unfortunately dark matter and dark energy are the father and mother of all woo-woos.

Of course not, they are the largest parts of standard cosmology, and have both been observed to high significance during the last year or so. (Bullet et cetera clusters for dark matter, the Integrated Sachs-Wolfe effect for dark energy.)

None of which applies to the “electric universe” pathetic pseudoscience.

The action is at the cell boundaries.

AFAIU DrFlimmer there aren’t any cell boundaries, as electrons will have to leak over the large distances involved to set up potentials. And I bet there aren’t any observational evidence of charged “cells”; I have asked for some time now.

Can you suggest how you would prevent current flow?

Absence of larger scale charge separation would do it, wouldn’t it? You would need local active mechanisms akin to cold plasma electrodes to drive a local current through, I think. That is btw how I understand currents gets going in our planets flux tubes, like the one connecting to Io.

Btw, those galactic magnetic fields were generated by rotational acceleration caused by gravitation, weren’t they? So how do you think they would overcome their generating gravity on larger scale, or on smaller scales as they were weak?

@[b]Nathan Myers[/b]
“@Don: Actually that’s madge’s son. But it’s genetic; I presume there are damaged genes on the X chromosome. Maybe the corresponding proteins could be provided, but you’d need to get the right cells to take them up. Someday the requisite genes might be packaged in a virus coat that targets at the right cells, and arranged to be expressed in the right amounts and places, but it doesn’t seem easy.”

Thanks for correcting to [b]Madge’s[/b] son. Sincere apology.

Umm, would genetic manipulation actually rectify the condition at the time of manipulation? Is there any surgical, medicational or other new techniques, other than genetic manipulation, which might remedy his conditon?

Hope you Labor Day Holiday enjoyed by you, your families, and friends.

@Torbjörn: If you were cared about the subject, you would know the papers well. If you were actually interested, you would already have located and read some. As it is you have revealed your intentions. If this were a scientific forum, citing papers would be both appropriate and obligatory, but it is just a fluffy telescope-pictures blog run by a former (or might-have-been?) scientist turned impresario. Do you really believe that galactic magnetic fields are generated just by “rotational acceleration caused by gravitation”?

@DrFlimmer: I wish to be clear: You can explain any observation with arbitrarily weak models if you are allowed to be selective enough about which observations you choose to explain, and to rely on enough arbitrary assumptions that you know no one in your community will question. That’s where astronomy stands, at present; the makings of a science are there, but squandered. The pictures are great, enough so that astronomy’s budgets are in no danger, but of course the pictures are ultimately the products of engineering, not science.

@Don: I have never heard of any sort of intervention that can help color blindness. Anyway it’s far from a debilitating condition, except in a very few fields. It really is rude, though, to produce graphics in which key indicators differ only by red vs. green.

As I just found out the debate even goes on in the other post about the “massive monsters”.
And right there I postet something where I tried to explain the existence of the very WEAK galactic magnetic field. I said this:

“In galaxies we have neutral, cold gas and a small amount of ionised gas (plasma). The collision between the free electrons and the neutral atoms is much more efficient than the collisions between the protrons and the neutral atoms. So we yield a charge separation. Due to the rotation of the galaxies the current is aligned which is important. So we have a current and we get magnetic fields which are very weak – as we observe in galaxies. It’s almost like a dynamo. (I don’t know if this is correct, but it should be close to it 😉 ).”

Yes we have some currents in the galaxy, but they are well explained by the rotation of the galaxy wich IS a gravitational effect. There is no other way of producing these currents. Because you would need a potential-difference or a gradient in the plasma which would cancel out itself over time, I would guess.
One other thing that comes to my mind is conservation of charge. If we assume (and I guess we can do it – since we observe it on earth…) that there were made equal amounts of positive and negative charge in the “creation” of the universe (maybe a BigBang….. – even a plasma universe should have been created eventually) then there is no reason for a current being the first thing “in the world” – because I don’t see a reason for a charge seperation or a gradient. So there were no currents and no magnetic fields. How did they just “popped” up?

Oh, and btw: The heating of the ISM is quite simple and has nothing to do with gravitation. It’s the “hot gas” streaming away from the stars (->solar wind) heating it up. I was wondering about the IGM. But I think gravitation CAN heat up a gas cloud. Turbulence is motion, and motion is heat. So gravitational encounters may produce enough turbulence to heat the thing up – but as I said, I am not sure about this.

@Torbjörn
Well, the “Ruhr-Uni” was very close to become a german “elite-university” but we failed 😉 . Of course, german elite-universities have nothing to with Harvard or that sort – they are just getting a little bit more money for the research. The “Ruhr-Uni” is quite ok, but the standing is not excellent, but it could be worse 😉 I’m happy here. And as we see: Our physicists aren’t so bad at all 😉

“If this were a scientific forum, citing papers would be both appropriate and obligatory, but it is just a fluffy telescope-pictures blog run by a former (or might-have-been?)”

Ah…is that why it was so hard to even get an encyclopedia citation from you in the “Massive Monster” thread? Because this is “just a fluffy telescope-pictures blog”? Oh, and a citation which you didn’t even read thoroughly?

Please don’t call others out for not providing scientific citations if you, yourself, are not willing to provide the same.

@Todd W.: I didn’t criticize anybody for not providing citations. I criticized dishonesty, and namecalling, and hypocritical hyping of woo-woo, and credulous acceptance of predecessors’ idle speculations, but I didn’t demand any citations.

@Todd W.: Oh, and it was hard to get me to provide a link to an encyclopedia article because it’s a waste of time to demand or to provide a link to an encyclopedia article. The encyclopedia is right there, just look at it.

@DrFlimmer: I don’t pretend to know where current might come from. When you find evidence of current (e.g. a magnetic field), you know it’s there, and then you may seek to discover its origins. Theories are useful, but they come last.

The implication in your post was that Torbjörn should back up his arguments with citations, that if his argument had any validity, he should provide some. To make such statements when you do not adhere to the same standard smacks of the very hypocrisy you criticize.

Oh, and it was hard to get me to provide a link to an encyclopedia article because it’s a waste of time to demand or to provide a link to an encyclopedia article. The encyclopedia is right there, just look at it.

Hmm. I actually don’t recall demanding a link to an encyclopedia article. I was asking for links to scientific articles. I asked Phil to provide the same. After repeated back-and-forths over the subject, you finally provided a link, but even then that link was to an encyclopedia article, not a published scientific paper, and by your own admission you hadn’t even read the article.

The ultimate result, rightly or wrongly, is that you appear to have a weak case. You make statements condemning the larger scientific community that is interested in the topic (astronomers) without providing anything to back up your arguments. When pressed for links, you have hemmed and hawed and have yet to produce anything solid. As I already have, I will admit again that I am not versed in this area, but your arguments sound very, very similar in style to those used by other fringe groups (Creationists, anti-vaxxers, etc.). To whit, “the ‘experts’ are wrong, I’m right, no question about it at all.”

The arguments on the other side, by contrast, have tended not to say that you are completely wrong, but that there are other explanations that work to describe the phenomena. Yes, some of the plasma theories apply, but not completely necessary to describe the situation. It strikes me as a much more compromising position open to change as new data emerges.

@Todd W: I explained quite a few times that, and why, asking for scientific articles about mundane facts is futile. Ask, instead, why Phil does his best to obscure those facts in his reporting, and to avoid applying them, and chooses instead name-calling and outright dishonesty (“anti-science”) when attention is called to them. Even if you are not equipped to evaluate the substance of a disagreement, you should recognize those as attempts to distract you, indicating a weak position.

Astronomy is only one branch of science, and has mores very different from most others. They seem to have taken to heart that none of their results actually matter, in any mundane sense, so long as they can provide pretty pictures and talk knowingly about them. As a result, they have become very cavalier about their foundational assumptions, and openly hostile to outsiders who call them into question.

The history of science is littered with the remains of insular communities. Behavioral and Freudian psychologists wasted the lives of whole generations of psychology students, and squandered the fees of generations of desperate patients. Thousands of paralysis victims died of old age and bedsores waiting for neuroscientists to reconsider the doctrine that nerves cannot regenerate. In this case, all that’s wasted are the careers of astronomy students, but that seems bad enough.

Given the nature of the debate just on here, it does not strike me as being a cut-and-dried issue as, say, the fact that I cannot walk through a solid wall. Walking through walls is something that I can test for myself. The nature of plasma in space is not. However, I can read what others have observed and do my utmost to gauge the validity of their research. If I don’t have some direct sources to reference on this, then all I, or anyone else reading these threads, can do is to weigh the opinions of the various posters.

Now, I have some basis for gauging the experience of at least one of these posters. Dr. Plait has mentioned in various places on this blog regarding what is studies and work has been. On the other hand, I know nothing about what your studies have been on this subject. Both of you sound knowledgeable about it, but I’m not just going to take your, or Dr. Plait’s, word.

So, again, given my position, as well as that of other readers, it is entirely reasonable to request links to articles that support the arguments. You say that it is a “mundane fact”, yet you have done nothing to bolster that contention. How many average people would consider it common or ordinary? The lazy or apathetic would just accept whichever argument sounds most coherent. The more curious would ask to see the evidence, even if the presenter says that it is ridiculous to ask for evidence for something so plain and obvious.

Since Dr. Plait made an initial claim and you made an opposing claim, I targeted both of you to provide links to support your respective claims. But, I will open it up and ask anyone arguing against you to also provide links to scientific articles that support their arguments.

There are no disputed claims here. I pointed out that it’s all plasma. Everybody else has agreed it’s all plasma. Phil insists on calling it “gas”, instead. The issue is, why insist on calling it gas when it’s not? DrFlimmer says that’s just how astronomers are, they like to call things what they’re not (e.g. calling oxygen “metal”). That’s fine within their little clubhouse — they can all wear funny hats, too, if they like — but this is a public forum, and when you say “gas”, people reasonably think you mean “gas”.

Still, it might be OK if Phil admitted that saying “gas” when he meant “plasma” was just a personal foible. Everybody has them (e.g. I like archaic ligatures). Instead, he attacked me and called me nasty names, and then, amazingly, insisted against all sense and reference books, more than once, that plasma really is just gas. Now, I’m an adult and can take being called names, but it makes me wonder what the name-caller and deliberate misleader is up to. Why does he insist on his misnomer, to the point of rhetorical violence? We can guess, but wouldn’t it be better if he revealed it himself?

One of the items that was in dispute in the “Massive” thread was dark matter and whether or not it exists. Phil has stated in various posts that dark matter is a current, likely explanation for the “missing mass” of the universe. You posted that dark matter does not exist and that the “missing mass” can be explained by plasma (IIRC). So, that is the topic I am referring to regarding disputed ideas.

Also, regarding the behavior of plasma in space (as opposed to in the lab or even in Earth’s atmosphere), that does seem to be an issue of disagreement in the threads.

Still, it might be OK if Phil admitted that saying “gas” when he meant “plasma” was just a personal foible. Everybody has them (e.g. I like archaic ligatures). Instead, he attacked me and called me nasty names, and then, amazingly, insisted against all sense and reference books, more than once, that plasma really is just gas. Now, I’m an adult and can take being called names, but it makes me wonder what the name-caller and deliberate misleader is up to. Why does he insist on his misnomer, to the point of rhetorical violence? We can guess, but wouldn’t it be better if he revealed it himself?

If you don’t like Dr. Phil Plait’s apples, why the bloody hell are you persistently shaking his tree?!

@Todd W.: Actually, I didn’t say dark matter doesn’t exist, or that “the missing mass” can be explained by plasma. I said the whole topic was speculation. Dark matter is about as interesting as epicycles or the Id; i.e. it’s not an observation, it doesn’t arise out of observations, it’s just an artifact of a failed theory. It hardly seems worth mentioning at all.

@Davidlpf: No, you just lied, trying to tar me as an antivaxxer. Dishonest name-calling, on cue. (How are those calculations coming along? Oh, gave up? Never started?) Quick, fetch the stick!

“i.e. it’s not an observation, it doesn’t arise out of observations, it’s just an artifact of a failed theory”

Sounds like you’re saying that dark matter doesn’t exist. Please provide some studies that show that dark matter i just an artifact of a failed theory, or that point up the flaws in the hypothesis of dark matter.

Love your blog but please, please, please can we fix these infuriating gremlins? (Or better go back to the old blog host /server / whatchyamacallit & just improve that? This ‘Discover’ one ain’t the best & ain’t really growing on me either – they need to fix it up too. Eg. some left margin at least for starters please!)

Oh well what I came here to post – again since it didn’t work first time was this :

Stellar expert James B. Kaler’s superluminously brilliant website (the source of the Zubeneschmali link quoted by the BA at the top here.) notes that one of the stars comprising Almach (Gamma –2 Andromedae) is also a green-ish (but via contrast?) star of type B8 :

“The orbit gives a combined mass for the three stars of 8.7 times that of the Sun which is consistent with advanced B8 and A0 dwarfs joined with a lower mass class A7 (or so) dwarf star about which nothing is known.”

So Almach or at least one of its components joins Zubenelgenubi in the B8 type “green” stars. Thus we have :

So could there be something to this B type green or green~ish stars thing and could the greenness of the Antares and Rasalgethi companions be at least partly intrinsic as well as contrast?

Although then again we have also got other B8 type stars that are NOT green notably Sirrah a.k.a. Apheratz (Alpha Andromedae) and Rigel A (B8 and blue) plus Rigel’s B & C two B9 & blue dwarfs. (Albeit though those dwarfs are, I think, spectroscopic not visual binary orbiting the main supergiant.)

Hmmm … Co-incidence or do some B type stars esp. B8 V really appear green? If so why only some & not others?

Suggestions or thoughts anyone?

(Link with Almach via Kaler’s site to be attempted to post here again next ..)

Incidentally, I imagine somebody smarter or at least better intertoob-webbing skills than me (& the latter at least is well almost everyone else here I’d guess) has already tried the closed brackets html code technique & smarter things already. Can’t the moderators or ‘Discover’ people or anyone fix it though? Seems not so far ..

Of course, there’s always the issue of what’s ‘blue’ to some folks could also be seen as ‘green’ by others!

Turquoise anyone? 😉

(Eg. the colour of the old ‘Lleyton House March team (notable drivers – Ivan Capelli & Maurico Gugelmin) back in late 1980’s – early 90’s F1 racing to use an, admittedly obscure, example that sticks in my mind.)

“@StevoR – You can also put the website in the “Website” box when you post, then just tell people to click on your name. It’s another way to get around the auto-moderation filter for hyperlinks.”

Thanks! I’ll try that! In fact see above! 😉

(The Almach link via Kaler’s stars site should now be there!)

Cheers! 😀

Hmm.. folks go also find Kaler’s stars site and form viewing that his Alkmach (Gamma Andromedae) page via the link to Zubeneschamali (hypertext ain’t it?) at the top of this item. But of course, now they don’t need to. I hope! 😉

@Todd W: Can you tell the difference between the statements “It doesn’t exist” and “I know of no reason to think it exists”? What sort of documentary evidence would you propose might be needed to support the latter, in general? I have already said that I don’t consider it interesting to talk about, except as an example, so I don’t propose to talk about it further. If you’re very interested in it, ask somebody else.

You say that it is just an artifact of a failed theory. If that is true, then dark matter does not really exist. If you maintain that it is just an artifact, then you must have something upon which to base your claim. Please share the information which led you to that conclusion of fact.

If it is just opinion, fine, but then you need to rework your statement to “I think that dark matter is just an artifact of a theory that I believe has failed,” and no more questions will be raised, at least from me, regarding citations.

So far, your comments on the subject have not appeared to be merely opinions, but rather assertions of fact.

@Todd W: It is a fact that I know of no reason to think it exists. It is also a fact that I know of no reason to believe in ghosts and goblins. As to whether it indicates failure… I pull over and change my tire only when it’s gone flat. Your experience might differ.

There you go. I would’ve said the colour of the car was also just fractionally more green than blue although right on the border of both.

What do others here think – green / blue or both?

Incidentally folks, when I’ve printed bits of this thread out they’ve all
been in bold as well as italics. So somethiong else odd is going on with it as well …

Nathan Myers Said on September 4th, 2008 at 4:14 pm :

“@Todd W: It is a fact that I know of no reason to think it exists. It is also a fact that I know of no reason to believe in ghosts and goblins. As to whether it indicates failure… I pull over and change my tire only when it’s gone flat. Your experience might differ.”

Being pedantic in F1 races & other forms of motorsport they generally
change tryes before they go flat! Even in normal life when you’re tyres get bald and worn people often change them before waiting for the flat to
occur .. 😉

Also while the reasons for believing in ghosts and goblins may be poor – anecdotal evidence, old stories and the like – reasons do exist, just not ones that would suffice to convince you. Not that I’m saying they do exist just that reasons -whether valid or spurious – for thinking they *might* exist do exist.

But like I said I’m being pedantic (& a bit humerous) here! 😉

As for Dark Matter well that’s another (fairly dark & murky itself) topic for another thread methinks …

3) Antares B – also a green or green~ish B class dwarf (B8?) but again in a multiple system & possible contrast effect with M1 Ia red supergiant –.

4) Rasalgethi B – also a B class dwarf (B8?) although again part of a multiple system & possible contrast effect with its M5 Ib red supergiant primary.

5) One of the stars in the Jewel box cluster mentioned in the other thread I think also a B-type star perhaps although I’m not too sure.

So could there be something to this B type green or green~ish stars thing and could the greenness of the Antares and Rasalgethi companions be at least partly intrinsic as well as contrast? Of coyurse there arealso counter-examples of many non-Green B-type stars but still ..

Also could the secular (historical times) variability, the apparent fade in Zubeneschmali’s brightness be connected with its greenness?

One idea : could Beta Librae – Zubeneschmali’s – fade be connected with the ejection of a cloud of gas (a super-sized Coronal Mass Ejection type event perhaps?) which has created a surrounding gas cloud that has transformed the star from sapphire to emerald in colour?

@Todd W: This blog isn’t really the sort of place to learn much of anything. Tell you what, from now on I’ll link my name (as above) to places that are better. I’m afraid there will be a bias toward biology, perhaps because biologists seem to be more aware of what’s amazing than in other fields, or just because more that is biological is amazing. Don’t expect to get any work done if you start following them.

I’ve been reading some (more) of Nathan Myers’ posts/comments, in response to Phil Plait’s blogs … wow, just wow.

Aside from the weaving and dodging, and aside from the specific content, I get the impression that, in NM’s view, astronomy is not a science and cannot be one … ever (exception: once probes visit something that was once solely the domain of astronomy, such as the Moon, remote observation can be supplemented by in situ research).

Would you care to say a few words, NM, on what you regard the criteria for assessing whether some piece of astronomical research is scientific or not are?

Back to plasmas, gas, fluid dynamics, etc.

The Sun is a big ball of plasma; to what extent, Nathan, is any study of the Sun unscientific if it does not explicitly and directly incorporate plasma fluid dynamics?

Specifically, are all the papers on the Sun and neutrino physics unscientific for not having explicitly incorporated PFD?